How do you become a copyeditor? Do you just wake up one day with a burning desire to make the distinction between em dashes and en dashes? Are you just that bossy?
Sometimes. But even if you are the pickiest grammarian known to humankind, you still need to learn the conventions of the field. How do you do that? There are good ways to learn how to be a copyeditor, and then there are the bad ways.
Bad Idea: You could just dive in without any experience.
No, no, no, no, no. Don’t do this. You’re going to fuck up your first assignment and then you will never get another.
Good Idea: Get some professional experience.
This doesn’t mean you have to be a copyeditor to become a copyeditor. But get an internship and spend some time in an editorial office. Do some minor proofreading for someone and witness how the editorial flow works.
Good Idea: Read up
Awesome. This will teach you the proofreading marks and the kinds of things copyeditors look for. Read the proofreading section of Chicago Manual of Style, and all of The Copyeditor’s Handbook and The Subversive Copy Editor.
Good Idea: Take a class.
There are a bunch of intro to copyediting or proofreading classes that are offered at universities and continuing education programs around the country.
Bad Idea: Practice on someone else’s proofreading project.
I once had a freelancer turn in a proofreading project that her husband had worked on. “He was an English major at XXXX College,” she said. “I trust him.” Well I didn’t. And a good thing too because he did a piss-poor job of proofreading the book I was working on. Note to married freelance wannabes: Work on your wife’s projects AFTER she turns it in to the publisher.
Good Idea: Be professional. Try not to annoy me.
How did you start working in your field? Would you recommend it?
Fangs and Clause 
I started by learning all I could about writing craft, editing for writer buddies, writing commercially, and following my nose when a fact needed checking. Eventually I became the go-to person for those who knew me, and a career found me. But I’m still learning. Something new. Every day. You can’t rest on your laurels in this biz.
So true. The rules change. New phrases come up. You forget the things you used to know.
I have recently become a go to person for the APA formatting of PhD theses… it even pays… but… Oh My Fucking God! How I hate the APA Manual.
And I should point out that I’m an atheist.
When you start swearing to a god you don’t believe in, then you know it’s bad. What makes you hate the APA manual so bad (besides the fact that half the shit that they want you to do is NOT IN THE MANUAL) but ON THEIR BLOG ONLINE)?
Er, half the shit they want you… bugger, you said besides that…
You know when the 7th edition (if that’s the most recent one, I fergit) went to print, there were over 35 major errors and they had to publish errata. So, yeah, great, wonderful. Job well done!
In my professional college writing tutor capacity, I use Diana Hacker’s The Writer’s Reference. For my professional editor capacity, I fucking swear a lot. And end up using Hacker.